Glycoproteic hormones, throxine, estradiol and prolactin profiles across the blood-cerebrospinal fluid (CSF) barrier in pregnancy

The blood-CSF barrier (BCB), as a component of the blood-brain barrier, is protective for the maternal brain. This study assesses estradiol, prolactin, glycoproteic hormones (hCG, FSH, LH, TSH) and thyroxine across the BCB in pregnancy after 38 weeks. Method. 35 pregnant women were simultaneously sampled in serum and CSF during caesarian section and compared to 27 non-pregnant fertile women undergoing surgery for benign gynecological disorders. The study was approved by the local Ethics Committee. Results were analysed as nonparametric variables. Compared to non-pregnant controls, we found high serum estradiol levels at term, also reflected in the CSF, while the CSF/serum ratio was non-significantly modified (median ratio 0.1 versus 0.1, p=NS). Prolactin showed a similar proportional increase in serum and CSF levels at term, with unmodified CSF/serum ratio (median ratio 0.14 versus 0.18, p=NS). hCG showed a similar profile across the BCB. FSH was significantly lower at term, but still conserved the CSF/serum ratio. LH was undetectable in pregnancy. In peripartum TSH showed a unique profile across the BCB as it was the only one showing an increased CSF/serum ratio compared to non-pregnant controls (median ratio 0.11 versus 0.04, p<0.0001). Thyroxine was significantly increased in both serum and CSF, and showed a CSF/serum ratio unmodified from non-pregnant women (median ratio 0.02 versus 0.02, p=NS). Conclusion. There is an increase of BCB permeablity for TSH in term pregnancy. The peripartum increase in estradiol and decrease in HCG could be involved. We suggest that the unique TSH profile maintains the necessary thyroxine levels in pregnancy at term.